Are Heart Rate Monitors Accurate?

Wearable heart rate monitors used to be reserved for the serious sportsman, but they are becoming more commonplace and we use them to monitor our health, but are heart rate monitors accurate?

Lots of people come and see me because they are worried about their heart rate.

They may have had palpitations, which is feeling their heart racing, or they may have noted that their heart rate monitor says they have got a very fast or very slow heart rate.

It is understandable to be concerned if your heart rate registers an abnormal reading, but the question is ‘are heart rate monitors accurate?’

The answer is ’yes and no’.

It depends on the actual device used. There are thousands of different ones on the market, which can use many different ways of measuring the heart rate.

A recent study has compared the effectiveness of wrist monitors.

They found the Apple watch and Polar monitors were pretty accurate at detecting abnormal fast rhythms – supraventricular tachycardias (SVT’s). For episodes over a minute, the Apple watch detected them all.

The Polar monitor got most of them, but the Garmin and Fitbit devices were much worse, detecting less than half of these episodes of SVT.

The accuracy for shorter episodes was less good for all, but the Apple and Polar devices picked up about 2/3rds of 15-60 second episodes.

The take home message is that the Apple and Polar monitors are excellent to pick up this problem.

However, if you have had palpitations and think your heart is going fast, don’t be reassured by a Garmin or Fitbit.

Also, these devices are not substitutes for medical grade monitoring with a device such as a Bardy Carnation or Zio patch, let alone an implanted Reveal LinQ monitor.

The other thing to consider, is that your heart rate is just one measure of how healthy your heart is. There can be quite a wide range of what is normal depending on your age, sex and general levels of fitness.

If you are having any symptoms, such as palpitations, chest pain or breathlessness, then it is important to get checked out and don’t rely on home testing kits.

You should contact your GP, or you can arrange a consultation directly with me either in person or by video call. I am happy to talk to patients without a GP referral and also work with all of the major insurance providers.

The small print – the devices used in this study were the Apple Watch, Fitbit Charge HR, Garmin Vivosmart HR and the Polar A360. All these devices use a technique called photoplethysmography. This uses a green led light. It measures the reflections of the light. The reflected light changes with blood flow which can allow the device to calculate the pulse rate. This study applies to SVT’s, and refers to their ability to detect the fast heart rate. The devices may have algorithms to detect other abnormal rhythms such as atrial fibrillation – these were not tested in this study.

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